System for producing oscillations



A. N. GOLDSMITH AND J. WEINBERGER.

' SYSTEM FOR PRODUCING OSCILLATIONS.

APPLICATION FILED MAR. 23, I918.

1 ,334,087, f Patented Mar. 16, 1920.

Fig.1.

AA A AAAAA Inventors: I fllfred. N.Goldsm1t.h Julius Weinberger,

Their Attorney- UNITED STATES PATENT OFFICE.

ALFRED N. GOLDSMITH AND JULIUS WEINBERG-ER, OF NEW YORK, N. Y.,ASSIGNORS TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK. I

SYSTEM FOR PRODUCING OSCILLATIONS.

3 To all whom it may concern:

Be it known that we, ALFRED N. GOLD- SMITH and Jams WEINBERGER, citizensof the United States, residing at New York, in the county of New York,State of New York, have invented certain new and useful Improvements in"Systems for Producing Oscillations, of which the following is aspecification.

. Our present lnvention relates to the production of electricaloscillations and particularly to the application of high frequencyoscillations to radio signaling systems.

It has been found that an electron discharge device comprising anincandescent cathode, a cooperating anode, and a discharge controllingmember or grid inclosed in an evacuated envelop may be employed forproducing high frequency oscillations which are suitable for radiosignaling purposes. It has also been found that when oscillationsproduced in this way are employed for radio transmission the simplestand most convenient way of applying them to the radiating system is toinclude the usual plate circuit inductance directly in the antennacircuit. We have found, however, that with the usual circuitarrangements employedfor producing oscillations with an electrondischarge device the efii ciency of operation depends largely upon thevalues of the capacity, inductance and resistance of the oscillatingcircuits. In other words, for any given device, there is a certainadjustment of the values of these constants which will give the maximumoutput and the maximum efliciency. When the antenna is made a part ofthe system which produces the oscillations the capacity and resistanceof the system are determined largely by the capacity and resistance ofthe antenna and the frequency of the oscillations is then adjusted tothe desired-value by varying the inductance. Under such conditions itwill be found thatthe values of capacity, resistance and inductance thusimposed are notthe values which would give maximumoutput and maximumefficiency for the particular device used.

The object of our invention is to overcome this disadvantage and providea system of connections whereby the constants of the oscillating systemmay be made independent of the antenna constants and may be ad-Specification of Letters Patent. t t 1 1920, Application filed March 23,1918. Serial No. 224,143.

justed' to those values which will give the best etficiency ofoperation.

glhe novel features which we believe to be characteristic of ourinvention are pointed out with particularity in the appended claims, theinvention itself, however, both as to its organization and method ofoperation can best be understood by reference to the followingdescription taken in connection with the accompanying drawing in whichFigure 1 illustrates the application of our invention to a transmittingsystem for radio telegraphy, and Fig. 2 shows its application to atransmitting'system for radio telephony.

As indicated in the drawing an electron discharge device 1 whichcomprises the usual incandescent cathode 2, plate-shaped anode?) andgrid 4, is employed for producing the high frequency oscillations whichare to be supplied to the antenna 5. In the the approximate middle point6 of an '1nductance 7 and the anode 3 is connected by means of thevariable connection 8 to another point in this inductance through .thecondenser 9. The grid 4 is connected to another point in the inductance7 on the opposite side of the-central point 6 by means of the variableconnection 10. The energy for producing the oscillations is supplied bya direct current generator 11 connected between cathode 2 and anode 3.It will be apparent that portions 12 and 13 of the inductance 7 whichare included in the plate and grid circuits respectively of the device 1are inductively coupled to each other and that therefore oscillationswill be produced in the circuits of the device. This coupling isvariable at will and its value may be chosen within certain limitswithout afiecting the operation. The frequency of oscillations may beadjusted by varying the condenser 9 and the points of connection 8 and10 andthe constants of the system at the same time may be adjusted togive the maximum efficiency of operation. The antenna 5 is connected toinductance 7 by the variable connection 14: and the central point 6 ofthe inductance is grounded at 15. Thus it will be seen that the portionof inductance 7 which is included in the plate circuit of the device isalso included in the antenna circuit and that the capacity of theantenna,

lent by the condenser 16 shown in dotted lines, will be in shunt to thisinductance. As a result it will be apparent that the capacity of theantenna forms a part of the system in which the oscillations areproduced and since this capacity is fixed it may not be possible tosecure the adjustment of the con-' stants of the system necessary forthe best efficiency of operation. To overcome this disadvantage wecompensate for the effect of the antenna capacity by the use of acapacity 17 which is connected in shunt to the. inductance 13 in thegrid circuit and which preferably has a value approximately equal to thevalue of the antenna capacity. When the final adjustments are made theportions '12 and 13 of the inductance 7 will prefer ably have an equalnumber of turns and v under these conditions the effect of the anradiofrequency choke coil is so designed that it is resonant to the frequencyof the oscillations produced and under these conditionsit will act as asubstantially infinite impedance to the high frequency current,

' and at the same time permit of the free passage of the direct currentwhich feeds the plate circuit.

In order to adapt the system which we have described for producingoscillations to the transmission of modulated signals, and particularlysignals modulated by speech currents, the current produced in atelephone transmitter 20 may be applied to the grid circuit of thedevice by means of an audio frequency transformer 21, as indicated inFig. 2. The secondary of thetrans former 21 18 preferably shunted by acondenser 22 in order to by-pass the high frequency component of thecurrent in the grid circuit.

The operation of this system is as follows: Suppose the device 1 isproducing sustained oscillations of a given amplitude in the antenna.When the telephone transmitter 20 is affected by sound waves voltagescorresponding to these waves are induced in the secondary of thetransformer 21 and thus directly impressed on the grid 4. The changes inrid potential cause exactly similar and much greater reactance voltagesto be produced across the audio frequency choke coil 23 in the circuitwhich supplies. the energy for producing oscillations. Therefore theplate voltage is varied as these reactance voltages add to or aresubtracted from the direct current 'voltage of the generator 11. Theradio frequency "0 energy output is directly proportional to the energyinput into the plate circuit of the device and the plate energy input isalmost directly proportional to the plate voltage. It is therefore clearthat as the 7 plate voltage is varied by the reactance voltages across23 the'radio frequency energy output is varied in almost exactproportion. These are the conditions sought for in radio telephony andthe method described gives extremely accurate and eflicient reproductionof speech as Well as being electrically efficient.

While we have described and illustrated our invention with especialreference to the transmission of telegraphic signals by the usual keyand to the transmission of sound waves by the aid of the usual telephonetransmitter, it will be apparent that our invention is by no meanslimited to the particular arrangements shown for controlling the antennacurrent, but that many other modifications may be made in the system ofconnections used without departing from the scope of the appendedclaims.

What we claim as new and desire to secure by Letters Patent of theUnited States, is

1. The combination in a system for producing electrical oscillations ofan electron discharge relay having inductively coupled plate-and gridcircuits, a third circuit which includes an inductance in the platecircuit of said relay and a capacity which shunts said plate circuitinductance, and a capacity connected in shunt to an inductance in thegrid circuit of said relay and having a value correspondingapproximately to the capacity of the third circuit.

2. The combination in a system for producing electrical oscillations ofan electron discharge relay having coupled plate and grid circuits, aradiating antenna connected to an inductance in the plate circuit ofsaid relay in such a way that the capacity of said antenna shunts saidplate circult inductance, and a capacity connected in shunt to aninductance in the grid circuit of said relay and having a valuecorresponding approximately to the capacity of the antenna.

3. The combination in a system for producing electrical oscillations ofan electron discharge relay having coupled plate and grid circuits, athird circuit which includes an inductance in the plate circuit of saidrelay and means for compensating for the capacity of the third circuitand thereby rendering the adjustment of the system in which oscillationsare produced independent of the capacity of the third circuit.

4. The combination in a radio signaling system of means for producingradio frequency oscillations comprislng an electron discharge relayhaving coupled plate and grid circuits, a radiating antenna directlyconnected to an inductance in the plate circuit of said relay and meansfor compensating for the capacity of the antenna and thereby renderingthe adjustment of the oscillation producing means independent of thecapacity of the antenna.

5. The combination in a system for producing electrical oscillations ofan electron discharge relay having a cathode, an anode and a grid, aninductance having its approximate central point grounded and connectedto the cathode of said relay, adjustable connections between the anodeand grid of said relay and points in said inductance on each side of thecentral point, whereby separate portions of said inductance are includedin the plate and grid circuits of the relay, a third circuit whichincludes the inductance of the plate circuit and a capacity in shunt tothe grid circuit inductance hav- 'ing a value correspondingapproximately to the capacity of the third circuit.

6. The combination in a system for producing electrical oscillations ofan electron discharge relay having a cathode, an anode and a grid, aninductance having its approximate central point grounded and connectedto the cathode of said relay, adjustable connections between the anodeand grid of said relay and points in said inductance on each side of thecentral point whereby separate portions of said inductance are includedin the plate and grid circuits of the relay, a radiating antennadirectly connected to the plate circuit inductance and a capacity inshunt to the grid circuit inductance having a value correspondingapproximately to the capacity of the antenna.

In witness whereof we have hereunto set our hands this 18th day ofMarch, 1918.

ALFRED N. GOLDSMITH. JULIUS WEINBERGER.

